Infection burden and immunological responses are equivalent for polymeric and metallic implant materials in vitro and in a murine model of fracture-related infection.

The development of an infection is a major complication for some patients with implanted biomaterials. Whether the material or surface composition of the used biomaterial influences infection has not been directly compared for key biomaterials currently in use in human patients. We conducted a thorough in vitro and in vivo investigation using titanium (Ti) and polyether-ether-ketone (PEEK) as both commercially available and as modified equivalents (surface polished Ti, and oxygen plasma treated PEEK). Complement activation and cytokine secretion of cell of the immune system was assessed in vitro for all materials in the absence and presence of bacterial stimulants. In a follow-up in vivo study, we monitored bacterial infection associated with clinically available and standard Ti and PEEK inoculated with Staphylococcus aureus. Complement activation was affected by material choice in the absence of bacterial stimulation, although the material based differences were largely lost upon bacterial stimulation. In the in vivo study, the bacterial burden, histological response and cytokine secretion suggests that there is no significant difference between both PEEK and Ti. In conclusion, the underlying material has a certain impact in the absence of bacterial stimulation, however, in the presence of bacterial stimulation, bacteria seem to dictate the responses in a manner that overshadows the influence of material surface properties. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1095-1106, 2019.

Safety and efficacy of incobotulinumtoxinA doses up to 800 U in limb spasticity: The TOWER study.

OBJECTIVE: To evaluate safety (primary objective) and efficacy of increasing doses (400 U up to 800 U) of incobotulinumtoxinA (Xeomin, Merz Pharmaceuticals GmbH) for patients with limb spasticity. METHODS: In this prospective, single-arm, dose-titration study (NCT01603459), patients (18-80 years) with spasticity due to cerebral causes, who were clinically deemed to require total doses of 800 U incobotulinumtoxinA, received 3 consecutive injection cycles (ICs) with 400 U, 600 U, and 600-800 U incobotulinumtoxinA, respectively, each followed by 12-16 weeks' observation. Outcomes included adverse events (AEs), antibody testing, Resistance to Passive Movement Scale (REPAS; based on the Ashworth Scale), and Goal Attainment Scale. RESULTS: In total, 155 patients were enrolled. IncobotulinumtoxinA dose escalation did not lead to an increased incidence of treatment-related AEs (IC1: 4.5%; IC2: 5.3%; IC3: 2.9%). No treatment-related serious AEs occurred. The most frequent AEs overall were falls (7.7%), nasopharyngitis, arthralgia, and diarrhea (6.5% each). Five patients (3.2%) discontinued due to AEs. No patient developed secondary nonresponse due to neutralizing antibodies. Mean (SD) REPAS score improvements from each injection to 4 weeks postinjection increased throughout the study (IC1: -4.6 [3.9]; IC2: -5.9 [4.2]; IC3: -7.1 [4.8]; p < 0.0001 for all). The proportion of patients achieving ≥3 (of 4) treatment goals also increased (IC1: 25.2%; IC2: 50.7%; IC3: 68.6%). CONCLUSION: Escalating incobotulinumtoxinA doses (400 U up to 800 U) did not compromise safety or tolerability, enabled treatment in a greater number of muscles/spasticity patterns, and was associated with increased treatment efficacy, improved muscle tone, and goal attainment. CLINICALTRIALSGOV IDENTIFIER: NCT01603459. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that, for patients with limb spasticity, escalating incobotulinumtoxinA doses (400 U up to 800 U) increases treatment efficacy without compromising safety or tolerability.

Monitoring immune responses in a mouse model of fracture fixation with and without Staphylococcus aureus osteomyelitis.

Post-traumatic bone fractures are commonly fixed with implanted devices to restore the anatomical position of bone fragments and aid in the healing process. Bacterial infection in this situation is a challenge for clinicians due to the need for aggressive antibiotic therapy, debridement of infected tissues, and the need to maintain fracture stability. The aim of this study was to monitor immune responses that occur during healing and during Staphylococcus aureus infection, in a clinically relevant murine model of fracture fixation. Skeletally mature C57bl/6 mice received a transverse osteotomy of the femur, which was treated with commercially available titanium fracture fixation plates and screws. In the absence of infection, healing of the fracture was complete within 35days and was characterized by elevated Interleukin (IL)-4 and Interferon-gamma secretion from bone-derived cells and expression of these same genes. In contrast, mice inoculated with S. aureus could not heal the fracture within the observation period and were found to develop typical signs of implant-associated bone infection, including biofilm formation on the implant and osteolysis of surrounding bone. The immune response to infection was characterized by a TH17-led bone response, and a pro-inflammatory cytokine-led Tumor necrosis factor (TNF)-α, Interleukin (IL)-1ß) soft tissue response, both of which were ineffectual in clearing implant related bone and soft tissue infections respectively. In this murine model, we characterize the kinetics of pro-inflammatory responses to infection, secondary to bone trauma and surgery. A divergent local immune polarization is evident in the infected versus non-infected animals, with the immune response ultimately unable to clear the S. aureus infection.

Mechanism of cell integration on biomaterial implant surfaces in the presence of bacterial contamination.

Bacterial contamination during biomaterial implantation is often unavoidable, yielding a combat between cells and bacteria. Here we aim to determine the modulatory function of bacterial components on stem-cell, fibroblast, and osteoblast adhesion to a titanium alloy, including the role of toll-like-receptors (TLRs). Presence of heat-sacrificed Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, or Pseudomonas aeruginosa induced dose and cell-type dependent responses. Stem-cells were most sensitive to bacterial presence, demonstrating decreased adhesion number yet increased adhesion effort with a relatively large focal adhesion contact area. Blocking TLRs had no effect on stem-cell adhesion in presence of S. aureus, but blocking both TLR2 and TLR4 induced an increased adhesion effort in presence of E. coli. Neither lipopolysaccharide, lipoteichoic acid, nor bacterial DNA provoked the same cell response as did whole bacteria. Herewith we suggest a new mechanism as to how biomaterials are integrated by cells despite the unavoidable presence of bacterial contamination. Stimulation of host cell integration of implant surfaces may open a new window to design new biomaterials with enhanced healing, thereby reducing the risk of biomaterial-associated infection of both "hardware-based" implants as well as of tissue-engineered constructs, known to suffer from similarly high infection risks as currently prevailing in "hardware-based" implants.

Antiadhesive polymer brush coating functionalized with antimicrobial and RGD peptides to reduce biofilm formation and enhance tissue integration.

This paper describes the synthesis and characterization of polymer-peptide conjugates to be used as infection-resistant coating for biomaterial implants and devices. Antiadhesive polymer brushes composed of block copolymer Pluronic F-127 (PF127) were functionalized with antimicrobial peptides (AMP), able to kill bacteria on contact, and arginine-glycine-aspartate (RGD) peptides to promote the adhesion and spreading of host tissue cells. The antiadhesive and antibacterial properties of the coating were investigated with three bacterial strains: Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. The ability of the coating to support mammalian cell growth was determined using human fibroblast cells. Coatings composed of the appropriate ratio of the functional components: PF127, PF127 modified with AMP, and PF127 modified with RGD showed good antiadhesive and bactericidal properties without hampering tissue compatibility.

An in vitro investigation of bacteria-osteoblast competition on oxygen plasma-modified PEEK.

Polyetheretherketone (PEEK) films were oxygen plasma treated to increase surface free energy and characterized by X-ray photoelectron microscopy, atomic force microscopy, and water contact angles. A parallel plate flow chamber was used to measure Staphylococcus epidermidis, Staphylococcus aureus, and U-2 OS osteosarcomal cell-line adhesion to the PEEK films in separate monocultures. In addition, bacteria and U-2 OS cells were cocultured to model competition between osteoblasts and contaminating bacteria for the test surfaces. Plasma treatment of the surfaces increased surface oxygen content and decreased the hydrophobicity of the materials, but did not lead to a significant difference in bacterial or U-2 OS cell adhesion in the monocultures. In the S. epidermidis coculture experiments, the U-2 OS cells adhered in greater numbers on the treated surfaces compared to the untreated PEEK and spread to a similar extent. However, in the presence of S. aureus, cell death of the U-2 OS occurred within 10 h on all surfaces. The results of this study suggest that oxygen plasma treatment of PEEK may maintain the ability of osteoblast-like cells to adhere and spread, even in the presence of S. epidermidis contamination, without increasing the risk of preoperative bacterial adhesion. Therefore, oxygen plasma-treated PEEK remains a promising method to improve implant surface free energy for osseointegration.

Infection resistance of degradable versus non-degradable biomaterials: an assessment of the potential mechanisms.

Extended life expectancy and medical development has led to an increased reliance on biomaterial implants and devices to support or restore human anatomy and function. However, the presence of an implanted biomaterial results in an increased susceptibility to infection. Due to the severity of the potential outcomes of biomaterial-associated infection, different strategies have been employed to reduce the infection risk. Interestingly, degradable biological materials demonstrate increased resistance to bacterial infection compared to non-degradable synthetic biomaterials. Current knowledge about the specific mechanisms of how degradable biological materials are afforded increased resistance to infection is limited. Therefore, in this paper a number of hypotheses to explain the decreased infection risk associated with the use of degradable versus non-degradable biomaterials are evaluated and discussed with reference to the present state of knowledge.